How many people smoke marijuana?

A recent government survey tells us:
Marijuana is the most frequently used illegal drug in the United States. Over 83 million Americans over the age of 12 have tried marijuana at least once.
Over 12 million had used the drug in the month before the survey.
Another survey, which is conducted yearly, includes students from 8th, 10th, and 12th grades. In 2001, the survey showed that 20 percent of 8th-graders have tried marijuana at least once, and by 10th grade, 20 percent are “current” users (that is, used within the past month.) Among 12th-graders, nearly 50 percent have tried marijuana/hash at least once, and about 22 percent were current users.